The Bioassay Core is a new entity, established 3 years ago, representing the consolidation of the Immunology Core and the Quality Control component of the Vector Core. The increasing complexity of the activities of the Vector Core and the expanding application of vectors for in vivo gene therapy in both small and large animals required very rigorous evaluation of all vector preparations. The Bioassay Core is directed by Dr. Guangping Gao who has been a leader in the development of novel vectors over the last decade. The Bioassay Core subjects all vectors produced in the Vector Core through a series of analyses to assure the purity, identity and potency of the preps. A senior member of Dr. Gao's staff serves as the Quality Assurance officer and audits assays and results. Criteria have been established for the release of vector from the Vector Core and are stratified in to two groups: vectors for in vitro or in vivo murine studies versus vectors destined for large animals such as dogs and nonhuman primates. The Bioassay Core also performs a number of assays to evaluate the innate and acquired immune responses to vectors with a focus on humoral immunity.